The content in question was footage of the 1970s Cambodian genocide that the parents of Central Valley congressional candidate Elizabeth Heng survived. Facebook allowed the ad to go back online Tuesday, after conservatives who were already upset about the company’s removal of content posted by right-wing conspiracy monger Alex Jones accused Facebook of censoring speech with which it disagrees.

Facebook, YouTube and Apple iTunes removed Jones’ content this week, saying it violated its rules against hate speech. Heng’s four-minute ad, however, was designed to be uplifting and personal, making Facebook’s initial decision to pull the ad difficult for the company to explain.

Heng, who is running against Rep. Jim Costa, D-Fresno, opened the ad with black-and-white photos of the Cambodian genocide under the Pol Pot regime of the 1970s, then explained how her parents narrowly avoided death and later came to the U.S.

“My parents did not have the luxury of blocking the horrific content from the reality of their lives during the rise of communism in Cambodia,” Heng wrote on Twitter last week as she rallied conservative leaders and media platforms against the ban. “Why does @facebook feel they have the right to censor that content in the land of #freespeech?”

Facebook said partisanship didn’t play a role in its decision. Initially, it said the ad was banned because Facebook doesn’t allow content that is “shocking, sensational, disrespectful or excessively violent.” Facebook restored the ad after executives deemed that the video contained historical imagery that was relevant to Heng’s story, the company said.

Facebook’s content policies have come under close scrutiny since it was revealed that Russian companies tied to the Kremlin bought ads and posted pages in 2016 intended to help Donald Trump’s presidential campaign. Media analysts said the handling of Heng’s ad shows that Facebook is struggling with its screening process for political content, with potentially dire consequences for the November elections.

“We have big tech companies umpiring our elections. And they’re not the umpires,” said Michael Cornfield, a George Washington University professor and expert on social media. “This goes back to the problem that we haven’t made up our minds whether to treat them like a public utility or a private media company.”

It took five days for Facebook to change its mind on Heng’s ad. Cornfield wondered what would happen if a controversial video was posted “in the last 72 hours of the campaign and Facebook didn’t decide right away (about whether to remove or restore it). That might affect a close election. Do we want that?”

“Users and politicians should really be concerned that these sorts of take-downs are happening at all,” McSherry said. “It’s the result of making (social media platforms) the self-appointed speech police.”

Making the situation even more confusing is that there aren’t consistent standards across social media platforms. While Facebook banned Heng’s video, Twitter and YouTube had no problems posting it.

Conservatives including House Majority Leader Kevin McCarthy, R-Bakersfield, jumped on the ban as an example of Facebook’s anti-conservative bias.

“Elizabeth Heng is a Republican woman,” McCarthy wrote on Twitter. “Her family survived the Communist genocide in Cambodia and came to America. Now Facebook is blocking her story.”

The ad starts with Heng, 33, describing how “in Cambodia under Pol Pot’s Khmer Rouge, being young and single often meant a gruesome life and likely death,” as images of skulls and dead bodies appear on the screen.

“They approached my father and in order to save his life, he said he was about to be married,” Heng says. “They asked him to whom. He pointed to the prettiest girl that he saw, having never spoken to her before. The soldiers approached her and she said, ‘Yes.’ They got married the very next day. Forty-one years later they’re still the happiest couple I know. Great things can come from great adversity.”

In a statement emailed to The Chronicle, Facebook said, “Upon further review, it is clear the video contains historical imagery relevant to the candidate’s story. We have since approved the ad and it is now running on Facebook.”

Even after the ban was lifted, Heng told The Chronicle on Tuesday that she was “angry in a lot of ways.”

“It took Facebook five full days to lift this arbitrary ban,” Heng said. “What about everybody else who is not able to summon a national wave of support to help them?

“I don’t think this would have been an issue if I were a liberal from Los Angeles,” Heng said. Facebook’s “algorithms are not conducive to conservative and diverse political thought.”

The Electronic Frontier Foundation’s McSherry, who has studied social media platforms for more than a decade, disagreed. “I do not think people take things down because of partisan bias,” she said. “They make mistakes all around.”

She testified in April before the House Judiciary Committee that “part of the problem is that a great deal of online content is not easy to classify quickly and automatically. Both machines and humans may struggle to tell the difference between disagreeable political speech and abuse, between fabricated propaganda and legitimate opinion, or between content that is legal in some jurisdictions and not others.”

Asked whether the controversy has drawn attention to her campaign, Heng, a first-time candidate, answered like a seasoned politician: “Regardless of what happens with Facebook, I’m going to keep fighting for my community. I’m not going to let some liberal tech company stop me.”

Joe Garofoli is the San Francisco Chronicle’s senior political writer, covering national and state politics. He has worked at The Chronicle since 2000 and in Bay Area journalism since 1992, when he left the Milwaukee Journal. He is the host of “It’s All Political,” The Chronicle’s political podcast. Catch it here: bit.ly/2LSAUjA

He has won numerous awards and covered everything from fashion to the Jeffrey Dahmer serial killings to two Olympic Games to his own vasectomy — which he discussed on NPR’s “Talk of the Nation” after being told he couldn’t say the word “balls” on the air. He regularly appears on Bay Area radio and TV talking politics and is available to entertain at bar mitzvahs and First Communions. He is a graduate of Northwestern University and a proud native of Pittsburgh. Go Steelers!